Rotary apparatus for testing instruments



April 21, 1959 R. E. BROWN 2,882,717

ROTARY APPARATUS FOR TESTING INSTRUMENTS I Filed Sept. 3, 1954 4 Sheets-Sheet l flf ya 1o RALPH E. BROWN,

INVENTOR. I

ATTORNEY April 21, 1959 Filed Sept. 5, 1954 R. E. BROWN 4 Sheets-Sheet '2 134 1 o 134 136 3' 115 12a 1 m 17 H I I]: 87 m9 234 214 216 39 i i 88 38 155 1 I m m 2 42 4' 2:2 145 I I m 37 i] 22 211 80b 152 i l m 191 165 4g 47 8 146 156 I RALPH E. BROWN, INVENTOR.

A TTORNE Y RE. BROWN ROTARY APPARATUS FOR TESTING INSTRUMENTS April 21, 1959 4 Sheets-Sheet 3 Filed Sept. 3, 1954 RALPH 8. BROWN,

IN VEN TOR.

BY /J) A TTORNE Y April 21, 1959 R. E. BROWN 2,832,717

ROTARY APPARATUS FOR TESTING INSTRUMENTS Filed Sept. 5, 1954 4 sheets sheet 4 5 mo 90 F1 7 as J d e W A l I 6994 I 75 96 95 so 71 i2 37 71 J m ,4 m

- RALPH E. BROWN,

IN VHV TOR.

A T TORNEY United States Patent ROTARY APPARATUS FOR TESTING INSTRUMENTS Ralph E. Brown, Los Angeles, Calif., assignor to Genisco, Inc., Los Angeles, Calif., a corporation Application September 3, 1954, Serial No. 454,104

19 Claims. (Cl. 73-1) This invention relates to variable-speed rotary apparatus and refers especially to rotary apparatus designed to provide controlled centrifugal forces for testing acceleration-responsive devices such as accelerometers, and for testing rotation-responsive devices such as gyroscopes and the like. The invention is directed to improvements for increasing the accuracy and convenience of operation of such an apparatus, as well as improvements for speeding up test procedures and for reducing the time and expense required for maintenance of the apparatus. The invention is further directed to the problem of testing devices for acceleration and rotation-responsiveness at pressures either substantially above or substantially below the ambient atmospheric pressure.

The presently preferred embodiment of the invention is a compact unit in a suitable housing, preferably an upright housing, designed to rest on the floor. The unit incorporates an electrically driven variable-displacement hydraulic pump coupled with a constant displacement hydraulic motor for the actuation of a horizontal turntable. The variable hydraulic transmission makes possible an infinite number of speed adjustments in a range which, for example, may extend from 20 r.p.m. to 1650 r.p.m.

The preferred embodiment of the invention includes a bypass in the hydraulic transmission under the control of a suitable relief valve that opens at a predetermined pressure for protection of the drive system against excessive inertia and dynamic loads. The relief valve may be adjusted, for example, to open at a fluid pressure that corresponds to a torque of 40 inch-lbs. on the turntable. A feature of the invention is that a ibraking force of substantially the same magnitude can be applied to the turntable simply by changing the displacement adjustment of the hydraulic motor to zero, to cause the hydraulic motor to act temporarily as a hydraulic pump against the resistance of the same relief valve. Thus with the hydraulic pump driven at a constant speed by an electric motor, and with the displacement adjustment of the pump at a setting to rotate the hydraulic motor and turntable at a relatively high rate, the turntable may be braked to a. quick stop independently of the electric motor.

A further feature of the preferred practice of the invention in this regard is the provision of both a main gradually operable pump-displacement control for varying the speed of the turntable by small increments and a second overriding quick-operable control for independently reducing the pump displacement to zero. The added overriding control not only permits use of the above described braking action to save time in decelerating the turntable but also makes it possible to maintain a selected speed setting of the main control from one test operation to another.

For testing devices under different pressures, the invention provides a test chamber for the turntable that is of fluid-tight construction and has conduit connections that permit the chamber to be evacuated. A problem is to provide such a chamber construction that affords adequate access to the turntable in preparation for tests.

'ice

The invention solves this problem by a stack of wall elements alternating with resilient sealing means, one of the wall elements being a removable cover for the chamber. A suitable pivoted arm is provided that not only carries the cover between test operations, but also serves to apply pressure to the assembled stack to make the resilient sealing means effective.

For accurate speed readings and adjustments, the invention combines a direct reading tachometer with a strobe arrangement that utilizes strobe indicia on the turntable in the sealed test chamber. The tachometer indicates the approximate speed of rotation, i.e., the approximate range of speed within about two percent accuracy, and the strobe arrangement reveals the precise speed in that range within about 0.1 percent accuracy.

One outer side of the housing of the preferred embodiment of the invention serves as a station for controlling and observing the tests carried out by the apparatus. The electrical motor is controlled from this station and both the main gradually operable speed-control of the hydraulic transmission and the second quick-acting speed-control are also manipulated at this station. A remote indicating dial for the tachometer is at the control station and the strobe indicia on the turntable in the sealed test chamber are made visible at the control station by a combination of window means and mirror means. In addition, a drum scale at the control station provides for quick conversion of r.p.m. and radii of gyration into G loadings.

By means of a slip ring assembly rotating with the tumtable and a cooperative stationary brush assembly instruments under test on the turntable may be connected with test circuits outside the test chamber as desired. Aside from attention to the level of the hydraulic fluid in the transmission system, only the slip rings and the brushes require periodic inspection. To facilitate such inspection and servicing, the preferred practice of the invention provides a novel fluid-tight bearing arrangement for the turntable, including a bearing unit which may be quickly and conveniently moved through the bottom wall of the test chamber. This bearing unit carries the brush assembly which is thus removable for inspection or displacement. The arrangement is such that the removal of the brush assembly also serves to expose the slip ring assembly for convenient access.

The various features and advantages of the invention will be readily apparent from the following detailed description considered with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative Figure 1 is a perspective view of the presently preferred embodiment of the invention;

Figure 2 is a vertical sectional view of the apparatus;

Figure 3 is a fragmentary sectional view showing the construction of the test chamber and the means for sealing the test chamber in fluid-tight manner;

Figure 4 is an enlarged sectional view of the bearing structure for the turntable apparatus;

Figure 5 is an enlarged fragment of Figure 2 showing a portion of the speed control mechanism, and

Figure 6 is a diagram of the hydraulic transmission system that is incorporated in the apparatus.

The embodiment of the invention illustrated in the drawings has a base plate 10 that is adapted to be anchored to the floor by suitable bolts (not shown). Mounted on the base plate is an open top housing having a front wall 11, two side walls 12 and a back wall 13. At least some of thees walls or portions thereof are removable for access to the interior of the housing.

The principal working parts of the apparatus include: a horizontal turntable, generally designated by numeral 17; an upright shaft 18 which supports and rotates the turntable; a constant-displacement hydraulic motor 20 3 having a shaft 21 that is connected to the turntable shaft by a suitable coupling 22; a variable-displacement pump 25 driven by a shaft 26; and 'an electric motor 30, the shaft of which is connected by a coupling 31 with the pump shaft'26.

These working parts are carried by support structure inside the housing which includes four horizontal plates, namely a lower plate 32 :(Figure 2) having a central opening 33 to surround the motor 30, a plate 34 having a central opening 35, a plate 36 (Figure 4) having a centralo'pening 37 and a plate 38 having a central opening 39. The two plates 36 and 38 surround an upright supineans or hearing unit 40 in the form of a generally cylindrical casting. The upper plate 38 constitutes the bottom wall of the test compartment or test chamber which encloses the turntable 17.

Ihe :motor 30 is carried by a ring 44 at its upper end and the ring in turn is mounted on the fixed plate 32 by shock-absorbing support elements 45. In the same way, a hydraulic transmission casing which is generally designated by numeral 46 and houses both the hydraulic motor 20 and the hydraulic pump 25 is carried by a ring 47 and is mounted'on the fixed support plate 34 by shock-absorbing "support elements 48. Thecasing 46 with the enclosed hydraulic pump and motor may be a Vickers coaxial hydraulic transmission, model TR3-HL3Fl3.

As best shown in Figure 4, the turntable 17 is centrally apertured and cut away to form an inner radial flange 50 that abuts the upper end of the turntable shaft 18. The turntable 17 is attached by screws 51 to a hub member 52 that is keyed onto the end of the turntable shaft -18. The upper end of the turntable shaft is of tubular configuration and is internally threaded to receive an end plug 53 which is formed with a non-circular opening 54 therethrough to receive a suitable tool. The lower end of the opening 54 is closed by a thin sheet metal member 55 that is attached to the plug by suitable screws 56 to form a stop for the tool used to turn the plug 53. The end plug 53 has a radial flange 57 which overlaps the radial flange 50 of the turntable 17. The turntable is formed with an annular recess 58 to seat a'suitable keeper ring 59 that overlaps the plug flange 57 and is anchored to the turntable by screws 60. The turntable I7 is suitably adapted for the mounting of objects thereon for test procedures and for this purpose may be provided with "numrous threaded bores -64.

The turntable shaft 18 carries an assembly ofslip rings and the upright support member or hearing casting 40 eai'ries a "corresponding brush assembly for cooperation with the ring assembly so that circuits may be completed to the instruments and devices under test on the turntable 17. In the construction shown, the slip ring assembly on the turntable shaft 13 comprises two groups of slip rings 65 carried by suitable sleeves '66 on the shaft. The brush assembly comprises two corresponding groups of brush 'elementstil mounted on two brush holders 68. The sleeves '66 carrying the slip rings 65 are removably mounted on the turntable shaft and the two holders '68 carrying the brush elements 67 are removably mounted on the bearing casting '40. Leads, not shown but intended to "connect the instruments undergoing test to the ring assemblies 65, are brought into the shaft 18 through the openings 69 from each ring assembly and are carried upwardly through the shaft and passed outwardly through the openings 69a formed in the upper end of the shaft 18 just beneath the hub member 52 as viewed in Figure 4 of the drawing.

In the now preferred practice of the present invention, to seal the upper end of the shaft 18 a suitable sealing material in the form of a slurry is poured into the upper end of the shaft after the conductors or leads for the instrument have been mounted in place. These leads substantially fill the bore of the shaft 18 and tend to hold "a large part of the sealing compound within the shaft adjacent the openings 6921. The particular sealing post section a.

compound used is one which, when set, will adhere not only to the leads or conductors, but also to the wall of the bore of the shaft 18 and the openings 69a to form a substantially fluid-tight sealing member filling the upper end of the bore of the shaft.

A feature of the invention is that the bearing casting 40 is removably supported brine fixed horizontal plate 36 and is dimensioned for removal'upward through the central opening 39 in the horizontal plate 38. It is apparent that with the turntable 17 removed from the upper end of the turntable shaft 18, the bearing casting 40 may "be lifted clear or the upper end of the shaft to permit full access to the brush elements '67 and that the removal of the bearing casting 40 from its normal position fully exposes the slip rings 65. Thus inspection of the slip rings and brush element is simplified and it is a simple matter to replace any of the slip rings and brush elements when ever necessary.

In the construction shown, the bearing casting 40 is carried by a heavy ring 70 that is mounted on the underside of the fixed plate 36 by means of cap screws 71, the bearing casting being centered by engagement with a concentric annular recess 72 on the upper surface of the ring. The heavy ring 70 also supports the outer race of a ball bearing 73 and the inner race of this ball bearing abuts a circumferential shoulder 74 of the turntable shaft 18 for rotary support of the shaft. A second ball bearing 75 is mounted in the upper end of the bearing casting 40 at the level of the upper fixed horizontal plate 38.

It is apparent that all of the operative parts of the apparatus are carried by the four fixed horizontal plates 32, 34, 36 and 38. Preferably this series of four plates is reinforced by a plurality of vertical posts 80 inside the housing. The vertical posts 80 extend upward from the base plate 10 and may be made in sections as shown in Figure 3.

Figure 3 shows a post section 80a engaging the under side of the horizontal plate 36 and a second post section 80b engaging the underside of the horizontal plate 38. The post section 80a has a reduced upper end 81't hat fits into a corresponding bore in the plate 36, and the lower end of the post section 80b is formed with a threaded stem 83 that screws into the upper end of the The upper post section 80b seats at its "upper end in a bore 'in the fixed horizontal plate 38 and is anchored to this plate in a fluid-tight manner by means of a suitable screw 85 and a sealing ring 36 that surrounds the screw.

In the particular construction shown in the drawings, the aperture 39 in the uppermost horizontal plate 38 at the bottom of the test compartment is closed by means 7 including a closure plate 87 which may be regarded as a s'ee'tibn of the plate or bottom Wall 38 of the test coinpartment. The closure plate 38 is in the form of a ring that rests upon a circumferential flange 88 of the bearing casting 40 and is attached thereto by suitable screws 90.

Preferably the test chamber that encloses a turntable 17 can be made fluid-tight, as heretofore stated. "For this purpose, the turntable shaft 18 must extend through the bottom wall 38 of the test chamber in a fluid-tight manner. In the construction shown in Figure '4, a suitable sealing ring 93 is mounted in a circumferential recess or groove 94 in the closure plate 87 and a second sealing ring 95 is mounted in an annular groove 96 in the bearing casting 40 under the closure plate. The required seal between the turntable shaft 18 and the bearing casting '40 is provided by an annular sealing means 97 'ein'- bracing the turntable shaft and a pair of sealing rings98 and 99, all three of which are carried by a retaining'ring T00 that is mounted on the upper end of the bearing casting '40 by suitable screws 101.

To provide the desired fluid-tight chamber for enclosing the turntable -I7, the present embodiment of the invention includes a wall assembly that cooperates with the ii bottom wall 38 of the chamber. This wall assembly may comprise a stack of wall members with interposed resilient sealing means, as best shown in Figure 3.

The wall assembly in Figure 3 comprises a peripheral or cylindrical wall member 105 to surround the turntable, a floating plate or wall member 106 having a central circular aperture 107, and a top wall or cover 108. The interposed resilient sealing means in the wall assembly comprises three channel-shaped rubber-like sealing rings, namely, a sealing ring 109 engaging the lower edge of the cylindrical wall member 105, a sealing ring 110 engaging the upper edge of the same cylindrical wall memher, and a third sealing ring 111 engaging the downwardly directed rim of the cover 108. It is apparent that this wall assembly may be placed under vertical pressure against the fixed plate 38 to seal the space enclosed by the wall assembly in a fluid-tight manner.

. Any suitable arrangement may be employed to exert the required downward sealing pressure on the chamber cover 108. As shown in Figure 3, the pressure applying means may comprise a suitable cantilever arm 115 that is both rotatably and slidably mounted on a pivot post 116. The pivot post 116, which is slidingly embraced by the floating wall member 106, has a reduced lower end 117 which extends through corresponding bores of the fixed plates 36 and 38 with a circumferential shoulder 118 of the pivot post resting on the upper surface of the plate 38. A spacer sleeve 119 surrounds the lower end of the pivot post between the two fixed plates 36 and 38 and a suitable nut 120 threaded onto the lower end of the pivot post abuts the under surface of the fixed plate 36.

The cantilever arm 115 comprises an upper metal bar 124 and a lower metal bar 125 of angular configuration, these two bars being united with a suitable bearing sleeve 126 that is mounted on the upper end of the pivot post 116 for rotation and axial movement thereon. A ball bearing 127 is seated in the upper end of the bearing sleeve 126 with the outer race of the ball bearing held in place by a flanged collar 128. The inner race of the ball bearing 127 embraces a manually operable pressure screw 130 in abutment with a downwardly directed circumferential shoulder 131 of the screw. The pressure screw 130, which has four radial handles 134, screws into a threaded bore 135 in the upper end of the pivot post 116. It is apparent that with the bearing sleeve 126 extending upward beyond the upper end of the pivot post 116, the pressure screw may be tightened manually to shift the bearing sleeve 126 downward on the pivot post, thereby to cause the cantilever arm 115 to exert the desired downward sealing pressure on the wall assembly.

Preferably the test chamber cover 108 is connected to the cantilever arm 115 for support thereby when the chamber cover is moved out of the way for access to the turn-table 17. As shown in Figure 3, the chamber cover 108 may be mounted on the cantilever arm 115 by a stud 136 that extends through suitable bores in the two bars 124 and 125 of the arm. The upper end of the stud 126 is provided with a nut 136 abutting the upper surface of the upper bar 124 and the intermediate portion of the stud is surrounded by a spacer sleeve 138 between the two bars. A bushing 139 on the stud abuts the lower face of the lower bar 125 and a nut 140 threaded onto the lower end of the stud cooperates with the bushing 139 for engagement with the chamber cover 108, as may be seen in Figure 3.

The front side of the housing of the apparatus comprises a control station and is provided with an inclined control panel 145, this panel being the forward wall of an auxiliary housing 146 mounted on the front housing wall 11. The panel 145 has a start button 147 to energize the motor 30 for clockwise rotation of the tumtable 17, a second start button 148 for energizing the motor in the opposite direction, and a stop button 149.

6 A suitable indicating lamp150 on the panel is energized when the motor is in operation.

The panel 145 is provided with a first or main speed control means in the form of a rotary disc 151 having a crank 152. A second control means is provided in the form of a handle adjacent one side of the panel. The manually rotatable crank 152 is intended to adjust the speed of rotation of the turntable 17 with precision and therefore is adapted to change the speed of rotation by small increments. The handle 155 is the overriding control that may serve in effect as a rapidly operable brake for abruptly decelerating the turntable. Both the control crank 152 and the control handle 155 operate a control arm or regulating means 156 of the hydraulic pump 25 to vary the displacement of the pump but the control handle 155 is adapted to return the control arm 156 to its zero-displacement position independently of the control crank 152.

The control arm 156 is mounted on the outer end of the shaft 157 that is rotatable to vary the displacement of the hydraulic pump thereby to vary the actuation of the hydraulic motor 20. The control arm 156 may be formed with a split end and provided with a pair of spaced bolts 158, as shown in Figure 5, to permit adjustment of the control arm relative to the shaft 157. The control arm 156 may be rocked clockwise as viewed in Figures 2 and 5 for increase in the displacement of the pump 25 and the control arm is biased in this clockwise direction by a suitable coiled spring 160. The spring is connected to the control arm 156 by a pin 161 that spans a recess 162 in the arm. The spring extends upward through a slot 163 in the horizontal plate 34 and the upper end of the spring engages a cross pin 164 in a similar slot 165 in the ring 47.

The spring 160 tends to move the outer end of the control arm 156 in an arcuate path but normally movement of the control arm along the path is limited by what may be termed a blocking member that is operatively connected to the manually rotatable disc. The blocking member 170 is provided with a rounded nose 171 for abutment by the control arm 156 and is in the form of a traveling nut mounted on a threaded portion 172 of a control shaft 173. Rotation of the traveling nut or blocking member 170 is prevented by a short rod 174 that is perpendicular to the control shaft 173. The blocking member 170 is apertured for sliding engagement with the rod 174 and the rod 174 is anchored at its opposite ends in a pair of support members 175. The support members 175 are in turn mounted on a suitable bracket member 176 that extends downward from the casing 46 that encloses the hydraulic transmission system. A pair of nuts 177 releasably tightened together on the threaded portion 172 of the control shaft, limit the downward movement of the blocking member 170 at the zero-displacement position of the control arm 156, and a second pair of similar nuts 178 limit the upward movement of the blocking member at the maximum-displacement position of the control arm.

The control shaft 173 has a reduced end portion 180 which extends through a bearing sleeve 181 in the support member 175 and which also extends through a ball bearing 182. A nut on the end of the control shaft together with a washer 186, cooperates with the ball bearing 182 to limit axial movement of the control shaft. The upper end of the control shaft 173, which extends into the auxiliary housing 146 and is journalled in the panel 145, carries the control crank 152.

It is apparent that clockwise rotation of the control crank 152 will cause the blocking member 170 to travel upward and that the spring 160 will cause the control arm 156 to follow the upward movement of the blocking member thereby increasing the displacement of the hydraulic pump for increased speed of rotation of the turntable 17. Conversely, counterclockwise rotation of the control crank 152 will move the blocking member down;

7 ward to retract the control 1 56 in o position to "the 'spring 160 for decreasing the rate of rotation of the turn-table. I

The control handle 155 may be operatively connected to 'the control arm 156 to return the control arm to its zero-displacement position to opposition to the spring 160 and independently of the blocking member 170. -In the Construction shown in the drawing, the control arm 156 carries a second'pin 190 in the previously mentioned recess 162 for pivotal connection to an operating rod 191, the operating rod being provided with a clevis 19 2 that extends into the recess and embraces the pin. The upper end of the operating rod 191 is controlled by a rocker arm 193 on a rocker shaft 194 that is journalled on suitable bearings -15 inside the auxiliary housing 146. "The rocker shaft 194 extends through the side wall of the auxiliary housing 146 and carries the control handle 155 at its outer end.

For approximate indications of the Speed of rotation of the turntable 17, the apparatus includes an electric tachometer'of a well-known type, which includes a generator 200 connected by an electric cable 201 with an instrument case 202 inside the auxiliary housing 146. The instrument case 202 provides a dial 203 (Figure 1) with pointer 204. A toggle-type reversing switch 205 positioned adjacent the dial 203 permits the electrical connections of the tachometer with the generator to be reversed when the direction of rotation of the turntable is reversed. 'An automatic switch can be used for this purpose, if desired.

The generator 200 is driven by the turntable shaft 18 but preferably is rotated at approximately half the speed of the shaft. For this purpose, a sheave 208, on the lower portion of the turntable shaft 18, is connected by a positive drive, cogged timing belt 209 to 'a larger sheave 210, the larger sheave being operatively connected to the generator 200. The larger sheave 210 is journalled between a pair of spaced plates 211 which are held together and -are anchored to the heavy ring 70 by means of suitablestuds 212. v

For precise determinations of the speed of the tumta'ble 17 within the approximate ranges indicated by the tachometer pointer 204, a suitable stroboscopic arrangemen't -is provided for observation by the operator at the control panel 145. In the present embodiment of the invention, the stroboscopic indicia or markings (not shown) are positioned in concentric rows n the undersid'e'of the turntable 17 for observation through 'a porthole 214 in the front wall 11 of the apparatus housing.

The stroboscopic markings are visible through the porthole by virtue of a sealed window'215 in the bottom wall 38 of "the test chamber and a suitably inclined mirror 216 immediately below the window. The mirror 216 is mounted on a suitable angular bracket 217. A 'stroboscopic lamp 218 is mounted on a bracket 219 in a position to illuminate the underside of the turntable 17 through the sealed window 215. The stroboscopic lamp 218 is'ehergi'zed by the usual 60-cycle line current and is controlled by 'a suitable switch 220 adjacent the porthole 214.

=Preferably suitable means is provided at the control station for convenient'conv'ersion of rpm. and radii of gyratidn'into'G loadings of three significant figures. For

thisipurp'ose, "a drum 222 (Figure 2) carrying a cylindrical'chart is mounted for rotation on a pair of brackets 224 inside the auxiliary housing 145. The values on the drum chart are visible through a narrow horizontal winhow on the panel 145, which window is provided with a cylindrical magnif in lens 226. Adjacent the magnifyi'ng lens is a horizontal scale 228 representing a range ofradii of gy'rations. The drum chart is controlled by 'a suitable knob 230 on-one side of'the auxiliary housing 146 so that the "operator ma quickly ascertain the -'G "valuefo'r eo'mbinatien 'of 'r.'p.'m. "and radii of 'gyration.

Suitable means is provided to: either evacuating "the test chamber or for filling the "chamber with a gaseous fluid under super-atmospheric pressure. For this purpose, at least one conduit extends the exterior of the test chamber through the plate or bottom wall '33. Preferably two such conduits are provided on opposite sides of "the test chamber. Figure 2 shows one conduit 232 for 'this purpose extending through a grommet 234 in the housing wall 13, the conduit terminating in "a lifting 236 in'the bottom chamber wall 38. A similar conduit on the 'otherside o'fthe test chamber is emitted in Figure 2 for the sake of clarity of illustration but is shown "at 238 in Figure 1.

In the hydraulic transmission system of the ap aratus shown diagrammatically in Figure 6, the hydraulic pump 25 is connected 'to the hydraulic motor 20 b a "High pressure discharge pipe 240fan'd a return pipe 242. A spring-loaded relief valve 244 has a relief passage 246 for return of hydraulic iiuid to a reservoir 248 and has two inlet passages, namely, an inlet passage 250 com nected to pipe 240 and an inlet passage 252 -connected to pipe 242. The relief valve 244 will open to receive fluid from either of the two inlet passages in response to rise in pressure in the relief passage to a magnitude that corresponds, for example, to a torque-of 40 inch lbs. on the turntable. -A pipe 254 having a check valve '256 connects the reservoir 248 with pipe 240 and for this purposemay be connected to the-corresponding inlet "passage 250. In like manner a pipe 258 halving a "check valve 260 connects the reservoir with pipe 242 and for this purpose may be connected to the second inlet passage 252.

In the normal operation of the hydraulic transmission for actuating the turntable 17, the hydraulic pum 25 continuously forces hydraulic fluid thr'ough thedischarge pipe 240 into the hydraulic motor 20, the hydraulic fluid returning through the return pipe 242. *If need for replenishment of the circulating fluid 'aris'es the consequent drop in pressure in the return pipe 242 Will -cause the check valve 260 to open automatically {for re renis'hing flow from the reservoir through pipe 258. If an inertia load -'or a dynamic load arises to an excessive magnitude, in this instance a magnitude exceeding 40' inch-lb's on the turntable 17, the relief Mtwill be o ened "by the' 'r'i'se in pressure in the inlet passage 250 and a portioniof the fluid will be returned to the'res'ervoir b'y' the relief passage 246. Thus a portion of the hydraulic fluid Willb'e bypassed from one side of the hydraulic pump to the other side through passage 250, relief valve 244, relief passage 246, reservoir 248, pipe 2'58, and p'assage'2'52 t'o the return pipe 242.

When the control arm 156 is positioned at zero-displacement for the hydraulic'pump .25,' the pumpiact's like a valve to cut off flow between the return pipe 24 2 land the discharge .pipe 240, but the hydraulic motor MI-continues to "rotate by virtue 'of the inertia 'of its rotating parts as well as the inertia of the loaded turntable. As a result the hydraulic motor 29 new functions as alpuuip drawing fluid from the reservoir 248 through .epipe 254, passage 25% and pipe 2 .9, the fluid being pumped back to the reservoir through pipe 242, passage -252, relief valve 244 and relief passage 246. Thus the resistance-of the relief valve provides a hydraulic braking action equivalent to a reverse torque of 40 inch-lbs.

The manner in which'the described apparatus operates for its'puipose ma 'be readily understood'from 'th'eforegoing description. I The electric motor for actuating the hydraulic transmission may be operated 'in eitherdirection by pressing either button "147 or button 148 and may be stopped subsequently by pressing button 149. Afteran initial warm-up p'e'riodfor stabilization or the temperature-of the hydraulic fluid, the hydraulic trans- "rnission *system comprising the hydraulic punip 25- and the hydraulic motor 20 will"rotate the turntable 17 at-a steady rate determined by adjustment of "the creamy erated control shaft 173. With the electric motor 30, rotating at constant speed and with the control arm 156 of the hydraulic transmission system at its zero-displacement position, the control crank 152 may be rotated clockwise to initiate notation of the turntable and to accelerate the turntable progressively to a desired speed. Any excessive loading of the hydraulic pump 25 by inertia or dynamic shock is prevented by the bypass valve 244 which opens whenever the pressure of the actuating hydraulic fluid exceeds a predetermined value.

To ascertain the speed of rotation of the turntable 17, the operator glances at the dial 203 which indicates the speed within a range of accuracy of approximately 2 percent and then observes the stroboscopic markings on the other side of the turntable 17 by looking into the porthole 214. The stroboscopic arrangement ascertains the precise speed within the two percent range, the possible error being narrowed to 0.1 percent. With a particular speed in mind, the operator may then manipulate the drum chart by means of the knob 230 to ascertain the equivalent G loading.

To stop the turntable 17 in a relatively abrupt manner for saving time at the end of a test period, the operator merely swings the control handle 155 counterclockwise as viewed in Figure 2, to return the control arm 156 to its zero-displacement position. At the zerodisplacement position of the control arm 156, flow of hydraulic fluid through the pump 25 is cut off and the continued rotation of the turntable 17 by momentum causes the hydraulic motor 20 to act as a pump against the resistance of the relief valve 244 as heretofore described. This action in the hydnaulic transmission will bring the loaded turntable to a dead :stop from high speed in a time period of about twenty-five seconds, whereas merely deenergizing the motor 30 without the benefit of the hydraulic braking action will cause the rotating parts to coast to a stop in a time period on the order of two minutes.

Since the setting of the control crank 152 is not disturbed when the control handle 155 is moved to its stop position for decelerating the turntable, returning the control crank to its normal position results in acceleration of the turntable again to the set speed. Thus no time is lost between test periods, a feature that is especially advantageous in carrying out a series of uniform tests.

When the test chamber is open, the chamber cover 108 is supported by the cantilever arm 115 in a position to one side of the housing to permit free access to the turntable 17. If a test is to be conducted under a pressure 7 that is either above or below the prevailing atmospheric pressure, the arm 115 is swung to place the chamber cover 108 in the position shown in Figures 2 and 3. The pressure screw 130 is then tightened down by manipulation of the radial handles 134 to place the three sealing rings 109, 110, and 111 under sufiicient pressure to make the test chamber fluid-tight.

My description in specific detail of the presently preferred embodiment of the invention, by way of example and to illustrate the principles involved, will suggest various changes, substitutions and other departures from my disclosure that properly lie within the spirit and scope of the appended claims.

I claim:

1. In a testing apparatus of the character described for rotating test objects, the combination of: a turntable to carry a test object; a hydraulic motor to drive said turntable; a power-actuated variable displacement pump to deliver actuating fluid to said motor at various rates for rotating the turntable at various rates; regulating means operatively connected to said pump and movable along a given path to vary the displacement of the pump for a range of speeds of said motor including zerodisplacement for zero speed, said regulating means being yieldingly biased to move in one direction along said path away from its zero-displacement position; means on said path blocking movement of said regulating means in said one direction and thereby normally determining the position of the regulating means; a first gradually operable control to vary the position of said blocking means along said path thereby to vary the position of said regulating means for adjusting the speed of said tumtable; and a second rapidly operable control means to move said regulating means in opposition to its bias in the other direction on said path to zero position independently of said blocking means for rapid deceleration of the turntable by the consequent pumping action of said hydraulic motor.

2. An apparatus as set forth in claim 1 in which said first control means includes screw means for varying the position of said blocking means.

3. An apparatus as set forth in claim 2 in which said regulating means includes a rocker arm; and in which a spring urges said rocker arm in said one direction.

4. An apparatus as set forth in claim 1 which includes a bypass across said hydraulic pump and a pressureresponsive relief valve controlling said bypass to prevent overloading the hydraulic pump.

5. In a testing apparatus of the character described for rotating test objects, the combination of: a substantially horizontal wall; shaft means extending upward through said wall in a fluid-tight manner; a turntable mounted on said shaft above said wall; a wall assembly above said horizontal wall to cooperate with said horizontal wall to enclose said turntable in a fluid-tight manner, said wall assembly including a peripheral wall member, a top wall member imposed on said peripheral wall member, and resilient sealing means under said peripheral wall member, at least a portion of said wall assembly being removable for access to said turntable; laterally extending retractable means normally overhanging said wall assembly to exert downward pressure on said top wall member for compression of said sealing means to make the space inside the wall assembly fluid-tight to permit said space to be maintained at a pressure different from the ambient atmospheric pressure; and fluid-passage means in communication with said space to permit the pressure therein to be changed.

6. An apparatus as set forth in claim 5 in which said retractable means includes an upright means at one side of said wall assembly and an arm on said upright means overhanging said wall assembly for downward pressure on the wall assembly.

7. An apparatus as set forth in claim 6 in which said arm is both rotatable and axially movable on said support means; and which includes means to vary the axial position of said arm on said upright means thereby to vary the pressure on said wall assembly.

8. An apparatus as set forth in claim 7 in which said arm includes a sleeve integral therewith and rotatably embracing said upright means; and which includes adjustable means in engagement with both said sleeve and said upright means to urge said sleeve downward on the upright means.

2. An apparatus as set forth in claim 5 which includes an anti-friction bearing having an outer race and an inner race, said outer race being seated in the upper end of said sleeve and said inner race being engaged by said adjustable means.

10. An apparatus as set forth in claim 5 in which said wall assembly includes both a removable cylindrical wall member normally surrounding said turntable and a separate top wall member; and in which said resilient means includes both a sealing ring effective between said two wall members and a sealing ring elfective between said cylindrical wall member and said horizontal wall. I

11. An apparatus as set forth in claim 10 which includes a floating horizontal plate extending between said cylindrical wall member and said top wall member, said floating plate having a central aperture of less diameter than the inside diameter of said cylindrical wall; and

assays? 11 when includes sealing means in contact with *the top and bottom faces of said floating plate.

1 2. In 'a testing apparatus of the character described for rdtating test objects, a combination of-z a testing chamber having a bottom wall with an aperture -therein; a-'driveshaft extending upward through said aperture; a turntable in said chamber removably mounted on said shaft; a slip ring assembly "on said shaft below said bottom wall; a brush assembly for cooperation with said slip ring assembly; removable means below said bottom wall to support said brush assembly, said brush assembly and support means being of less horizontal cross-sectional dimension than said aperture whereby with said turntable removed from the upper end of said 'driveshaft, said support means may be removed through said aperture for inspection :or replacement or said brush assembly; and removable means to close said aperture and to ro- 't atably embrace said shaft.

13. In a testing apparatus of the character described for rotating testobje'cts, a combination of a testing chamber having a bottom wall with an aperture therein; a driveshaftextending upward through'said aperture; a 'turntable in said chamber removably 'mounted on said shaft; aslip ring assembly on said shaft below said bottom wall; lower sup ort means spaced below-said bottom wall to support s'aid shaft at a'firs't lower level; an upright support means removably mounted on said lower support means and extending upward towards said aperture, said upright means supporting said shaft at a'second-up'per level; means for-closing said aperture, said closing means being normally connected with said upright support'means and being in engagement with said bottom wall to stabilize the upright support means; and a brush assembly carried by said upright support means for cooperation with said slip ring assembly, said upright support means and brush assembly being of less horizontal cross sectional dimension than said aperture whereby said upright support means may be lifted upward through said aperture for inspection and replacement of said brush assembly.

14. in a testing apparatus of the character described for rotating test objects, a combination of: a substantially horizontal wall having a removable portion to form an aperture therein; a shaft extending upward through said removable wall portion; a turntable on said shaft above said horizontal wall; a slip ring assembly on saidshaft below said horizontal wall; a brush assembly below said horizontal wall for cooperation with said slip ring ass'embly,'said brush assembly being removable through said aperture; means to form a fluid-tight seal between'said removable wall portion and the remainder of said horizontal wall and to form a fluid-tight seal between said removable wall portion and said shaft; a wall assembly above said horizontal wall of larger cross-sectional dimension than said aperture to cooperate with said horizontal wall around said aperture to enclose a 'space around 'saidturntable in a fluid-tight manner to permit said space to be maintained at a pressure dilferent from theambient atmospheric pressure, said wall assembly including a pcripheral wall surrounding said turntable and a top wall normallyspaced above said peripheral wall; resilientsealingmeans in said wall assembly to seal said space in response to compression of the wall assembly against horizontal wall; fluid passage means in communication with said space for changing the pressure therein; and retractable means to exert downward pressure on said wall assembly for compression of the wall assembly against said horizontal wall.

15. An "apparatus as set forth in claim 14 which includesa lower support means spaced below said horizontal wall, and includes a hollow upright support means our rounding said shaft and removably mounted 'on said lower support means, said hollow support means supporting said brush assembly and being dimensioned for :removal together with the brush assembly through said aperture, said removable 'portion of said horizontal wall being supported by said hollow support means.

16. 'In a testing apparatus of the character described for rotating test objects, the combination of: a turntable to carry a-te'st object; a'hydraulic motor operatively connected with said turntable;a power-actuated variable displacement hydraulic pump having its intake side conne'ctedto the discharge side of said hydraulic motor and its discharges ide connected to the intake side of the hydraulic motor for actuation thereof; a hydraulic reservoir connected "to the intake side of said hydraulic motor through a check valve; means'including a spring loaded relief valve connecting the discharge side of said bydraulic motor with the reservoir whereby adjustment 'of said "hydraulic pump to zero displacement while said hydraulic motor is rotating cuts off flow through 'the hydraulic motor-and causes the hydraulic motor to function as a pump to circulate the fluid through said reservoir against the resistance of said relief valve for braking action on the turntable; a first control for varying the displacement of said hydraulic pump gradually; and a second control independent of said first control for rapid adjustment of said hydraulic pump to zero displacement.

l7. lna testing apparatus, the combination of: a-rturntable providing a support surface to carry objects for testingpachamber enclosing said turntable to cut off objects thereon from the atmosphere and to subject the objects to pressure different from atmospheric pressure, said chamber including a fixed transverse bottom wall below the turntable, an upright removable wall of circular plan configuration extending upward 'from said bottom wall to a level above the turntable, a top wall and resilient sealin'g means effective between the walls; a power-driven vertical rotary support means supporting said turntable and extending downward therefrom through said bottom wall in a sealed manner; and means to place said walls underpressure to make said resilient sealing meanseffective, said pressure 'means including means overhanging said top wall to 'pressdownward on the top wall.

18. A combination as set forth in claim l7in whichsaid overhanging means is a cantilever arm, pivoted to .swing out of theway when the walls of the-chamber are separated for access to the'chamber.

l9. A combination as set forth in'claim 18 which :includes screw means acting on the pivoted end of said arm to place said walls-under pressure.

ReferencesCited tin the file of'this patent UNITED STATES PATENTS 1,889,128 McClintock Nov. 29, 1932 "1,910,054 "Rayburn May 23, 1933 2,097,436 Bennetch Nov. 2, 1937 2,148,277 Rose Feb.'2l, 1,939 2,407,996 Nie's Sept. 24, 1946 "2,4 IO,'l"55 Fall; Get. 29, 1946 2,447,330 Grebmeier Aug. 17, 1948 2,465,437 Engelhardt Mar. 29, 1949 2,608,344 Pickels Aug. 126, 1952 2,670,898 Pickels- Mar. 2, 1954 OTHER REFERENCES Publication entitled The-Genisco G Accelerator, receivedin Divbsb, US. Patent 'Ofiice, Jan. 31, 1952. 

